1. Technical Field
This invention relates generally to piston assemblies for use in small engine or automotive engine applications, and more particularly to the construction and method of attachment of a skirt to the piston assembly.
2. Related Art
Articulated pistons for small engine and/or automotive applications have the skirt formed separately from the crown and joined in articulated manner through the wrist pin. The crown has an upper ring belt portion in which a plurality of ring grooves are cut for accommodating rings of the piston. A pair of pin boss portions depend from the upper ring belt portion and are formed with an aligned pin bore for receiving a wrist pin to connect a wrist pin to a connecting rod. The crown of the piston is usually fabricated of steel. The articulated skirt of the piston is often fabricated of aluminum. The skirt is formed with a set of pin bores which align with the pin bores of the pin bosses to receive the wrist pin for connecting the skirt to the crown. Typically, the pin bores in the skirt have a circumferential groove formed therein for receiving a spring clip to retain the pin within the pin bores of the skirt and the pin bores of the pin bosses. In this way, the skirt is connected to the crown through the wrist pin such that the skirt is able to pivot slightly relative to the crown about the axis of the wrist pin and bores.
According to one construction of the invention, a piston assembly for an internal combustion engine comprises a piston body having a head and a pair of pin bosses depending from the head having a pair of pin bores aligned along a pin bore axis. The assembly further comprises a piston skirt having a pair of opposed skirt portions and a pair of opposed side wall portions joining the skirt portions. At least one skirt retainer is supported on at least one of the side walls, wherein the skirt retainer is biased axially inwardly along the pin bore axis in register with a corresponding one of the pin bores to connect the piston skirt to the pin bosses.
Another aspect of the invention provides a method of attaching a piston skirt in a piston assembly for an internal combustion engine. The method comprises the steps of providing a piston body having a pair of pin bosses depending from the end with a pair of pin bores aligned along a pin bore axis, and providing a piston skirt having a pair of opposed skirt portions and a pair of opposed side wall portions joining the skirt portions with at least one skirt retainer supported on one of the side walls. The piston skirt is attached to the pin bosses by guiding the skirt over free ends of the pin bosses and causing the skirt retainer to deflect outwardly and inwardly into register with the pin bores as the skirt snaps into position.
The invention has an advantage of decreasing the number of component parts required for assembly of a piston skirt within a piston assembly.
The invention has a further advantage of reducing both the associated costs in manufacturing the piston skirt, and also in reducing the total component costs of the piston assembly.
A further advantage is offered by improving the efficiencies in assembly of the piston assembly, and thus has an associated advantage of reducing the total assembly costs of the piston assembly.
Another advantage of the invention is that the piston skirt can be mounted on the piston body by simply pushing the skirt into engagement with the piston body.
Another advantage of the invention is that it is of relatively simple design and applicable to a wide range of internal combustion engine sizes and applications.